1. Field of the Invention
The present invention relates to a flat-type fluorescent lamp with a flat emission surface. More particularly, the invention relates to a flat-type fluorescent lamp, an illumination unit using the lamp, and a Liquid-Crystal Display (LCD) device equipped with the lamp as its backlight, which make it possible to narrow the frame area of a LCD device and to widen its display area.
2. Description of the Related Art
Conventionally, illumination units are used to form the edge-type or direct-type backlights of LCD devices.
With the edge-light type backlight, a cylindrical fluorescent lamp is located apart from a LCD panel to extend along one edge of the panel. The lamp is not overlapped with the rear surface of the panel. A light guide plate, which is made of acrylic resin, is provided near the fluorescent lamp to guide the light from the lamp toward the rear of the panel. A diffuser sheet is provided near the light guide plate to diffuse the light emitted from the plate, thereby relaxing the unevenness of the light emitted from the plate. Thus, approximately even light is illuminated to the rear surface of the panel.
The edge-light type backlight has the following disadvantages:
First, the light from the fluorescent lamp is difficult to be guided to the rear surface of the panel efficiently and uniformly. This difficulty increases with the widening display area of LCD devices. Second, since the fluorescent lamp is located in the picture-frame area of LCD devices, the edge-light type backlight is unfavorable from the viewpoint of narrowing the picture-frame area.
With the direct-light type backlight, a lamp house is formed at the rear of the LCD panel, in which several cylindrical fluorescent lamps are arranged. If the lamps are located too close to the panel, the light from the lamps is locally illuminated to the rear surface of the panel, which means that the light has uneven brightness. To avoid this problem, the lamps need to be located to have a certain distance from the panel and at the same time, a diffuser plate is essentially provided between the lamps and the panel, thereby diffusing the light from the lamps. Thus, the direct-type backlight has a disadvantage that it is difficult to cope with the requirement of thinning LCD devices.
Flat-type fluorescent lamps are fluorescent lamps having a flat emission surface and have the basic structure that a pair of opposing plates is joined together with an intervening frame member, thereby forming a container. A gaseous substance, such as an inert gas and a mixture of an inert gas and gaseous mercury (Hg), is confined in the container.
Flat-type fluorescent lamps can be used as the direct-type backlight of LCD devices and therefore, they have an advantage that means for guiding the light from the lamp to the LCD panels is unnecessary. Since the emission surface can be opposed to the whole display area of the panel, there is another advantage that brightness unevenness is difficult to be observed even if the lamps are close to the panel. Accordingly, flat-type fluorescent lamps are expected as a technique that meets the requirement of widening and thinning of LCD devices.
Next, a prior-art LCD device equipped with a prior-art flat-type fluorescent lamp as its backlight is explained below with reference to FIGS. 1 and 2A and 2B. FIG. 1 is an exploded perspective view of the prior-art device, where the flat-type fluorescent lamp is partially cut away. FIG. 2A is a cross-sectional view of the assembled prior-art device along the line IIAxe2x80x94IIA in FIG. 1. FIG. 2B is a partial, enlarged cross-sectional view of the assembled prior-art device of FIG. 2.
As seen from FIGS. 1 and 2A and 2B, the prior-art flat-type fluorescent lamp 120 comprises a rectangular emission-side plate 101, a rectangular electrode-side plate 102, and a rectangular frame member 103 that intervenes between the plates 101 and 102 and that has a rectangular window at its center. The plates 101 and 102 are entirely overlapped with each other by way of the member 103 in such a way that the contour of the plate 101 accords with that of the plate 102. The rectangular outer edges (peripheral areas) of the plates 101 and 102 are placed outside the member 103. Electrodes 104 are formed on the inner surface of the plate 102 by a screen printing method or the like. The ends of part of the electrodes 104 are extended to the outside of the member 103 on the inner surface of the plate 102, forming four electrode terminals 107 (i.e., an anode terminal 107a, a cathode terminal 107b, a cathode terminal 107c, and an anode terminal 107d).
The prior-art LCD device shown in FIGS. 1 and 2A and 2B comprises a LCD panel 108, the prior-art flat-type fluorescent lamp 120 as the backlight, a rectangular front chassi 109, a rectangular center chassi 110, and a rectangular rear chassi 111. The panel 108 is located on the emission side of the lamp 120. The peripheral area of the panel 108 is sandwiched and held by the front and center chassis 109 and 110, as shown in FIGS. 2A and 2B.
The front chassi 109 has a frame-like shape with a rectangular window at its center. The peripheral area of the chassi 109 is bent at a right angle to form its sidewalls. The chassi 109 forms the front picture-frame area of the LCD device and the side faces thereof.
The center chassi 110 has a frame-like shape with a rectangular window at its center. The peripheral area of the chassi 110 is bent at a right angle to form its sidewalls. The chassi 110, which is located between the panel 108 and lamp 120, holds the lamp 120 with its sidewalls in such a way as to surround the lamp 120.
The rear chassi 111 has a rectangular bottom that forms the rear surface of the LCD device. The peripheral area of the chassi 111 is bent at a right angle at the whole edge of the bottom to form its sidewalls. The chassi 111 is located to cover the electrode-side plate 102 of the lamp 120.
These three chassis 109, 110 and 111 are combined together to enclose the panel 108 and the lamp 120. As shown in FIGS. 2A and 2B, a circuit board 112 is mounted on the opposite surface of the rear chassi 111 to the lamp 120 (i.e., the rear surface of the LCD device. The board 112 includes an inverter circuit and other necessary circuits formed thereon.
As shown in FIG. 2B, a fluorescent material layer 105 is formed on the inner surface of the emission-side plate 101 of the lamp 120. The plate 101 is formed by a transparent glass plate, on which the emission surface of the lamp 120 is formed. The emission-side plate 101 and the electrode-side plate 102 are coupled with each other by way of the frame member 103 with frit glass (i.e., glass with low-melting point) 114, forming a closed container with a shape of rectangular parallelepiped. A gaseous substance 106 (e.g., an inert gas) is confined into the container at a pressure of approximately 10 kPa to 100 kPa. A specific voltage is applied to the substance 106 by way of the electrodes 104.
As clearly shown in FIG. 1, an opening 115 is formed at the sidewall of the rear chassi 111. The opening 115 extends to the bottom of the chassi 111. Another opening 116 is formed at the sidewall of the center chassi 110. These openings 115 and 116 are overlapped with each other to form a cable window 117 for allowing cables to reach the inside of the assembly of the chassis 109, 110, and 111.
As clearly shown in FIGS. 1, 2A and 2B, each of the anode terminals 107a and 107d and the cathode terminals 107b and 107c is connected to one end of each cable 113 with a solder 118. The other end of each cable 113 is connected to the circuit board 112 by way of a connector. The circuits (e.g., the inverter circuit) formed on the board 112 control the electric power applied to the gaseous substance 106 by way of the cables 113.
The cables 113 are placed in such a way as to run through the inner space that is located outside the frame member 103 and that intervenes between the plates 101 and 102 and then, they are collected at the cable window 117. These cables 113 thus collected are taken out of the space through the window 117 to the rear side of the LCD device, where the outer ends of the cables 117 are connected to the board 112.
If an appropriate voltage is applied across the electrodes 104 of the flat-type fluorescent lamp 120, ultraviolet (UV) rays are excited and emitted due to discharge of the gaseous substance 106 in the container. The UV rays thus emitted will collide with the fluorescent material layer 105 in the container, emitting visible light. The visible light thus emitted will penetrate through the emission-side plate 1 of the lamp 120 and reach the LCD panel 108. As a result, images are shown on the display area of the LCD device.
In addition, typically, a dielectric layer (not shown) is formed on the inner surface of the electrode-side plate 1 to cover the electrodes 104. A reflection layer (not shown) is further formed on the dielectric layer. An optical sheet (not shown) like a light diffuser plate is usually placed on the emission surface of the lamp 120.
To prevent unfavorable deformation and damage due to thermal stress, the emission-side plate 101, the electrode-side plate 102, the frame member 103, and the frit glass 114 are made of appropriate materials whose thermal expansion coefficients are close to each other, respectively. The plate 102 needs not be transparent. However, it is usual that the plate 102 is made of the same glass material as the plate 101. The member 103 may be made of glass or ceramic. The front, center, and rear chassis 109, 110, and 111 are usually formed by aluminum (Al) plates.
Typical dimensions of the prior-art device are as follows:
The thickness of each of the plates 101 and 102 is approximately 2 mm. The thickness and width of the frame member 103 are approximately 4 mm and approximately 4 mm, respectively. The width of the peripheral area of each of the plates 101 and 102 that is outside the member 103 is approximately 5 mm. The size of the cable window 117 (i.e., the distance from the side face of the plate 102 to the inner side face of the front chassi 109) is approximately 2 mm.
The center chassi 110 has a function of sustaining the fluorescent lamp 120 and the LCD panel 108 (and the diffuser plate, if any) and positioning them. This is to match the position of the display area of the panel 108 with that of the emission area of the lamp 120. The chassi 110 has a rectangular protrusion 119 to position the panel 108 in such a way as to contact the corresponding edge of the panel 108.
The function of the chassi 110 may be realized with a frame-shaped sustaining member located inside the chassi 110. In this case, the sustaining member, which is made of synthetic resin such as polycarbonate, sustains the lamp 120 (and the diffuser plate, if any) within the window of the sustaining member and at the same time, sustains the panel 108 with a protrusion (like the protrusion 119) that penetrates through the window of the chassi 110.
The above-described prior-art flat-type fluorescent lamp 120 and the prior-art LCD device have the following problems:
First, the ends of the cables 113 are connected to the electrode terminals 107 and then, the cables 113 are placed to run through the inner space that is located outside the frame member 103 and that intervenes between the plates 101 and 102. Thereafter, the cables 113 are collected at the cable window 117 and taken out of the space through the window 117 to the rear side of the LCD device. The outer ends of the cables 117 are connected to the circuit board 112 on the rear side of the device. Thus, there is a problem that wiring, connection, and assembly operations of the device are troublesome and that the necessary length of the cables 113 is large.
Second, since the cable window 117 is necessarily formed between the electrode-side plate 102 and the front chassi 109, there is another problem that the structure is disadvantageous from the viewpoint of narrowing the picture-frame area.
Third, to place the outer ends of the electrode terminals 107 outside the frame member 103, the plate 102 needs to be formed in such a way that the peripheral area of the plate 102 is located outside the member 103. Thus, there is a further problem that the structure is disadvantageous from the viewpoint of narrowing the picture-frame area at this point also.
Furthermore, the Japanese Non-Examined Patent Publication No. 9-172128 published in 1997 discloses a mounting structure of an integrated circuit (IC). In this prior-art structure, a U-shaped dielectric case with a conductor is attached to the edge of a semiconductor (IC) chip, thereby decreasing the necessary wiring area around the chip. Thus, the necessary mounting area for the chip is reduced.
The Japanese Non-Examined Patent Publication No. 58-137236 published in 1983 discloses a hybrid IC structure. In this prior-art structure, a U-shaped electrode is attached to the edge of a wiring board, thereby converting the board a surface-mounting type. Thus, vertical useless space of the board is eliminated to thereby make the IC more compact.
However, the structures disclosed by these two Japanese Publications have no relationship with the flat-type fluorescent lamp. They disclose no application methods of the structures to the lamps of this type. As a result, the above-identified problems are difficult or unable to be solved.
The present invention was created to solve the above-identified problems of the prior-art lamp 20 and the prior-art LCD device shown in FIGS. 1 and 2A and 2B.
An object of the present invention is to provide a flat-type fluorescent lamp, an illumination unit, and a LCD device that make it possible to narrow the picture-frame area and to widen the emission area of light.
Another object of the present invention is to provide a flat-type fluorescent lamp, an illumination unit, and a LCD device that facilitate their wiring, connection and assembly operations.
Still another object of the present invention is to provide a flat-type fluorescent lamp, an illumination unit, and a LCD device that lower their fabrication cost.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
According to a first aspect of the invention, a flat-type fluorescent lamp is provided, which comprises:
(a) a container having a first plate, a second plate, and a frame member;
the first and second plates being opposed to each other and fixed together with the frame member in such a way as to have a specific distance between the first and second plates;
the first plate forming a flat emission surface;
(b) a gaseous substance confined in the container;
(c) a fluorescent material layer formed on an inner surface of the container;
(d) electrodes formed on an inner surface of the second plate; and
(e) a conductor member attached to the second plate in such a way as to extend along the inner surface of the second plate and an outer edge face thereof;
a first end of the conductor member being contacted with a terminal part of the electrodes;
a second end of the conductor member being located outside the second plate.
With the flat-type fluorescent lamp according to the first aspect of the invention, the conductor member is attached to the second plate in such a way as to extend along the inner surface of the second plate and an outer edge face thereof. One end of the conductor member is contacted with a terminal part of the electrodes while the other end of the conductor member is located outside the second plate.
Therefore, the cable window 117 of the prior-art LCD device is unnecessary and thus, the picture-frame area can be narrowed. Also, the problem that the wiring, connection, and assembly operations of the cables 28 are troublesome is solved and as a result, these operations are facilitated.
For example, even after the lamp according to the first aspect is built in the chassis of a LCD device, the connection operation of the cables is possible. This means that the connection part of the cables can be easily checked with naked eyes and easily repaired, which is an additional advantage.
Because of the improvement of these operations, the fabrication cost is expected to be lower. Since the cables can be connected to the end of the conductor member located on the outside of the container, the necessary length of the cables can be reduced. This contributes to cost down as well.
In a preferred embodiment of the lamp according to the first aspect of the invention, the conductor member is U-shaped in cross section. The second end of the conductor member is extended inwardly along an outer surface of the second plate. In this embodiment, the second end of the conductor member extended along the outer surface of the second plate serves as an external terminal and therefore, there is an additional advantage that space is saved around the external terminal and that easy and reliable connection of the external terminal to the cable or a circuit board placed outside the container is realized.
In another preferred embodiment of the lamp according to the first aspect of the invention, the first end of the conductor member is sandwiched by the second plate and the frame member. In this embodiment, since the first end of the conductor member is sandwiched by the second plate and the frame member, the conductor member can be held without protruding the edge of the second plate from the frame member. The terminal part of the electrodes and the conductor member can be contacted with each other between the second plate and the frame member or on the inside of the frame member. Thus, the edge of the second plate needs not be protruded to the outside of the frame member, which means that the picture-frame area of the lamp can be narrowed.
Moreover, since the first end of the conductor member is sandwiched by the second plate and the frame member, they can be securely fixed together with a connecting material such as frit glass. Thus, there is an additional advantage that the supportability of the conductor member is improved compared with the case where the conductor member is supported by connecting the conductor member to the terminal part of the electrodes with a conductive connecting material such as a solder and a conductive resin paste. For example, when the conductor member is supported by connecting the conductor member to the terminal part of the electrodes with a conductive connecting material, there is a possibility that other members or tools contact the conductor member on the outside, resulting in cracks at the connection part or detachment of the conductor member. This possibility is eliminated in this embodiment.
In still another preferred embodiment of the lamp according to the first aspect of the invention, a depression or recess is formed at a location of the second plate or the frame member near the conductor member. In this embodiment, when the depression or recess is formed at a location of the second plate, the first end of the conductor member is placed in the depression or recess and thus, the connection surface of the second plate will be flat. Therefore, there is an additional advantage that the dimensional accuracy between the first and second plates coupled with the frame member is prevented from degrading.
If the depression or recess is not formed at a location of the second plate, the conductor member will form a protrusion at the inner surface of the second plate. In this case, the dimensional accuracy between the first and second plates coupled with the frame member will degrade due to the protrusion. However, by forming the depression or recess at a location of the frame member, this problem is avoided.
In a further preferred embodiment of the lamp according to the first aspect of the invention, a circuit board having an electrode terminal is additionally provided on a side of an outer surface of the second plate. The electrode terminal of the circuit board is contacted with the second end of the conductor member. In this embodiment, since the electrode terminal of the circuit board is contacted with the second end of the conductor member, the electrode terminal of the circuit board is electrically connected to the second end of the conductor member without any cable. Thus, there is an additional advantage that the fabrication cost and the workload for connection and wiring operations are lowered by the cost of cable.
In a still further preferred embodiment of the lamp according to the first aspect of the invention, one of the electrode terminal and the conductor member has a part with spring function. The part with spring function is contactable with the other of the electrode terminal and the conductor member. In this embodiment, the electrode terminal and the conductor member are contacted with each other by way of the part with spring function. Thus, there is an additional advantage that electrical connection between the electrode terminal and the conductor member is carried out by a simple operation.
In a still further preferred embodiment of the lamp according to the first aspect of the invention, a chassi covering an outer surface of the second plate, and a circuit board having an electrode terminal and mounted on the chassi are additionally provided. The circuit board and the conductor member are fixed with a screw at the electrode terminal. In this embodiment, there is an additional advantage that the circuit board and the conductor member are securely combined together and that the wiring, connection, and assembly operations are facilitated.
In a still further preferred embodiment of the lamp according to the first aspect of the invention, a resin chassi covering an outer surface of the second plate, a circuit board having an electrode terminal and mounted on the chassi, and a circuit pattern placed on the chassi are additionally provided. The chassi includes first and second female screws located apart from each other. The circuit pattern extends from the first female screw to the second female screw. The electrode terminal of the chassi and the conductor member are overlapped and fixed by engaging a first male screw with the first female screw. The second end of the conductor member and the chassi are overlapped and fixed by engaging a second male screw with the second female screw.
In this embodiment, there is an additional advantage that even if the circuit board and the conductor member are built in with a considerable distance due to restriction about the size and/or mounting position of the board, the circuit board and the conductor member can be electrically connected each other. There is another additional advantage that the circuit board, the wiring pattern, and the conductor member are securely combined together and that the wiring, connection, and assembly operations are facilitated.
In a further preferred embodiment of the lamp according to the fourth aspect of the invention, an outer face of the frame member, an outer side face of the first plate, and an outer side face of the second plate form an approximately flat sidewall of the lamp. In this embodiment, there is an additional advantage that the picture-frame area is narrowed because the edges of the first and second plates do not protrude from the frame member.
Preferably, the sidewall of the lamp is approximately perpendicular to the emission surface. If the sidewall of the lamp is considerably oblique to the emission surface, the picture-frame area is expanded.
According to a second aspect of the invention, another flat-type fluorescent lamp is provided, which comprises:
(a) a containert having a first plate, a second plate, and a frame member;
the first and second plates being opposed to each other and fixed together with the frame member in such a way as to have a specific distance between the first and second plates;
the first plate forming a flat emission surface;
(b) a gaseous substance confined in the container;
(c) a fluorescent material layer formed on an inner surface of the container; and
(d) electrodes for applying a voltage to the gaseous substance;
wherein an inner edge of the frame member on a side of the first plate is shifted outwardly from an inner edge of the frame member on a side of the second plate.
With the flat-type fluorescent lamp according to the second aspect of the invention, the inner edge of the frame member on the side of the first plate is shifted outwardly from the inner edge of the frame member on the side of the second plate and thus, the discharge space in the container expands toward the first plate (i.e., the emission surface) from the second plate. Therefore, the emission area is expanded and the picture-frame area around the emission area is narrowed.
In a preferred embodiment of the lamp according to the second aspect of the invention, the frame member has a trapezoidal cross section. In this embodiment, there is an additional advantage that the mechanical strength of the frame member (and therefore, the mechanical strength of the lamp itself) is increased.
In another preferred embodiment of the lamp according to the second aspect of the invention, an outer face of the frame member, an outer side face of the first plate, and an outer side face of the second plate form an approximately flat sidewall of the lamp. In this embodiment, there is an additional advantage that the picture-frame area is narrowed because the edges of the first and second plates do not protrude from the frame member.
Preferably, the sidewall of the lamp is approximately perpendicular to the emission surface. If the sidewall of the lamp is considerably oblique to the emission surface, the picture-frame area is expanded.
According to a third aspect of the invention, still another flat-type fluorescent lamp is provided, which comprises:
(a) a container having a first plate, a second plate, and a frame member;
the first and second plates being opposed to each other and fixed together with the frame member in such a way as to have a specific distance between the first and second plates;
the first plate forming a flat emission surface;
(b) a gaseous substance confined in the container;
(c) a fluorescent material layer formed on an inner surface of the container; and
(d) electrodes formed on an inner surface of the second plate;
the electrodes having a terminal part;
wherein the frame member has a recess for exposing the terminal part from the frame member outwardly;
and wherein the recess is located in a peripheral area of the frame member.
With the flat-type fluorescent lamp according to the third aspect of the invention, even if the edge of the second plate does not protrude outward from the frame member, the terminal part of the electrodes can be exposed from the frame member by way of its recess. Thus, the picture-frame area of the lamp can be narrowed.
In a preferred embodiment of the lamp according to the third aspect of the invention, an outer face of the frame member, an outer side face of the first plate, and an outer side face of the second plate form an approximately flat sidewall of the lamp. In this embodiment, there is an additional advantage that the picture-frame area is narrowed because the edges of the first and second plates do not protrude from the frame member.
Preferably, the sidewall of the lamp is approximately perpendicular to the emission surface. If the sidewall of the lamp is considerably oblique to the emission surface, the picture-frame area is expanded.
According to a fourth aspect of the invention, a further flat-type fluorescent lamp is provided, which comprises:
(a) a container having a first plate, a second plate, and a frame member;
the first and second plates being opposed to each other and fixed together with the frame member in such a way as to have a specific distance between the first and second plates;
the first plate forming a flat emission surface;
(b) a gaseous substance confined in the container;
(c) a fluorescent material layer formed on an inner surface of the container; and
(d) electrodes formed on an inner surface of the second plate;
wherein an inner edge of the frame member on a side of the first plate is shifted outwardly from an inner edge of the frame member on a side of the second plate;
and wherein an outer edge of the frame member on the side of the second plate is shifted inwardly from an outer edge of the frame member on the side of the first plate.
With the flat-type fluorescent lamp according to the fourth aspect of the invention, the inner edge of the frame member on the side of the first plate is shifted outwardly from the inner edge of the frame member on the side of the second plate. Thus, the discharge space in the container expands toward the first plate (i.e., the emission surface) from the second plate. Therefore, the emission area is expanded and the picture-frame area around the emission area is narrowed.
Moreover, the outer edge of the frame member on the side of the second plate is shifted inwardly from the outer edge of the frame member on the side of the first plate. Thus, a space is formed at an end of the inner surface of the second plate, which is outside the frame member. This means that a space applicable to exposing the terminal part of the electrodes is obtained along with the expanded emission area.
In a preferred embodiment of the lamp according to the fourth aspect of the invention, the frame member has a parallelogrammatic cross section. The inner face of the frame member and the second plate are at an acute angle. In this embodiment, there is an additional advantage that the frame member is easily processed mechanically.
In another preferred embodiment of the lamp according to the fourth aspect of the invention, an additional fluorescent material layer or a reflection layer is additionally formed on the inner face of the frame member. In this embodiment, because the additional fluorescent material layer emits light, the total amount of emission of light is increased in the vicinity of the frame member. Alternately, because the reflection layer suppresses the loss of UV rays due to collision to the frame member, the total amount of emission of light is increased in the vicinity of the frame member. Thus, there is an additional advantage that brightness insufficiency near the inner face of the frame member is eliminated in the discharge space in the container. This leads to increase in the effective emission area and decrease in picture-frame area.
Preferably, the fluorescent material of the fluorescent material layer in the container is formed to contact the frame member. This is to increase the amount of emission near the frame member.
According to a fifth aspect of the invention, an illumination unit is provided, which comprises one of the flat-type fluorescent lamps according to the first to fourth aspects.
With the illumination unit according to the fifth aspect of the invention, because one of the flat-type fluorescent lamps according to the first to fourth aspects is used, there are the advantages that (i) the picture-frame area is narrowed and the emission area is widened, (ii) the wiring, connection and assembly operations are facilitated, and (iii) the fabrication cost is lowered. Therefore, the illumination unit has improved uniformity of brightness and is light-weight and compact, which makes it possible to apply the unit versatile fields and/or purposes.
According to a sixth aspect of the invention, a LCD device is provided, which comprises one of the flat-type fluorescent lamps according to the first to fourth aspects and a LCD panel.
With the LCD device according to the sixth aspect of the invention, because one of the flat-type fluorescent lamps according to the first to fourth aspects is used, there are the advantages that (i) the picture-frame area is narrowed, (ii) the wiring, connection and assembly operations are facilitated, and (iii) the fabrication cost is lowered.